INFLUENCE OF THE NUCLEAR SUBSTITUTION ON THE SENSITIZED PHOTOOXIDATION OF MODEL COMPOUNDS FOR PHENOLIC-TYPE PESTICIDES

The dye-sensitized (singlet molecular oxygen-mediated photo-oxidation of a series of substituted model compounds for phenolic-type pesticide s was studied in several solvents in the alkaline range. From a kineti c point of view, the feasibility to regulate the environmental photo-o xidative degradation by means of the incorporation of electron- withdr awing or electron-releasing substituents in the phenolic nucleous was demonstrated. The photo-oxidability varies from relatively high quantu m yields values (0.11 in the most favourable cases for 2,6-dimethyl-4- bromophenol in organic solvent) to non-reactivity (for highly deactiva ted compounds such as 2,4-dinitrophenol).